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Investigate one of the Factors Affecting the Electrical resistance of a Wire.

Extracts from this document...

Introduction

To Investigate one of the Factors Affecting the Electrical resistance of a Wire

Introduction

In this investigation, I will investigate the electrical resistance of a wire. I will investigate what factors have the power to change electrical resistance and the theory behind it. In order to provide evidence of my statements, I will conduct an experiment. This experiment involves passing a flow of current though different lengths of metal wires of the same material. I will repeat the test to increase accuracy, then I will record my findings in a table of results. I will revise these results and produce an analysis.

Theory and Prediction

Metals conduct electricity because of the free electrons inside. Free electrons are basically electrons, which are not in orbit of the nucleus.

This means that they are free to move. These free electrons are what carry the charge and without these, no electricity can be conducted. Usually, electrons move randomly. When there is a potential difference, all electrons move in an orderly fashion towards the positive side because electrons are negative and negative attracts positive.

The electrical resistance of a wire is basically when the flow of current is decreased by a certain factor. The electrical resistance of a wire can be altered by four different factors. These factors are the length of the wire, the thickness of the wire, the temperature of the wire and the material of the wire.  

The thickness of a wire can significantly alter the electrical resistance.

...read more.

Middle

80

85

90

95

100

I feel this is a good table of results because it is immensely easy to read from and it will contain a large amount of information.

Theory

The theory of Ohm’s Law is “The amount of current flowing in a circuit made up of pure resistances is directly proportional to the electromotive forces impressed on the circuit and inversely proportional to the total resistance of the circuit.”

Source: http://webhome.idirect.com/~jadams/electronics/ohm.html

Basically, Ohm’s Law means a steady increase in voltage, in a circuit with constant resistance, produces a constant linear rise in current. Secondly, A steady increase in resistance, in a circuit with constant voltage, produces a progressively weaker current. To show this in more detail, I found some more data, which gives me much more information.

Preliminary Work

Length (mm)

L=1mm

Readings

(2 d.p)

V

(Volts/V)

I

(Amps/A)

R

(Ohms/   )

5

1.18

2.22

0.53

10

1.64

1.91

0.86

15

1.99

1.67

1.19

20

2.27

1.49

1.52

25

2.49

1.34

1.86

30

2.67

1.22

2.19

35

2.82

1.12

2.52

40

2.95

1.03

2.86

45

3.06

0.96

3.19

50

3.15

0.90

3.50

55

3.24

0.84

3.86

60

3.31

0.76

4.36

65

3.38

0.75

4.51

70

3.34

0.71

4.70

75

3.49

0.68

5.13

80

3.54

0.64

5.53

85

3.58

0.61

5.87

90

3.62

0.59

6.14

95

3.66

0.56

6.54

100

3.69

0.54

6.83

At first glances, it seems that my prediction is indeed correct. However, this table cannot be used as concrete evidence as it has only one set of readings. I will carry out another test, this time with three readings. I will calculate the averages and this will be much more accurate.

You may notice that in this table it says 4v rather than the 2v I proposed to use.

...read more.

Conclusion

Length of wire (mm)

Resistance (Ohms/   )

50

1.83

100

3.42

200

4.80

400

8.33

800

20.00

The table above shows us that as the length of the wire doubles, the resistance of the wire approximately doubles. This proves my earlier statement that length is directly proportional to resistance. The reason my results are not that accurate is because I did not use a digital ammeter. I found the readings on the ammeter difficult to read and as the lowest reading on the ammeter was 0.2 amps so my last five results were all 0.2 amps, which I am sure, is not correct. If I was in possession of a digital ammeter, my readings will be clear and simple. Unfortunately,

none were available and my results were to some degree, inaccurate.

Evaluation

I thoroughly enjoyed this investigation. I also found it very easy and interesting. There were some aspects I did not understand when the task was first set but it all became clear when I started the investigation.

The accuracy of my investigation was not perfect. I did not have a digital ammeter or voltmeter, which meant it was difficult to read and it would have been less accurate. Also, looking at the ammeter and voltmeter from different angles would give different readings so this may have also affected my results. I can also place a lot of the blame on myself. Firstly I only repeated the test once. To increase accuracy, I could have repeated the test many times giving me a large number of results, which would certainly improve accuracy.    

it appears to be a different reading and this would have made my results, to some degree, inaccurate.

...read more.

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